The goals of the proposed research are to determine the mechanism, location, and function of the breakdown of phosphatidylinositol and of the formation and continuous turnover of phosphatidic acid which occur in cell membranes in response to neurotransmitters and hormones. Responses to acetylcholine will be studied in two highly specialized tissue - the exocrine pancreas and the avian salt gland. Primary areas of investigation are: 1. The subcellular location of phosphatidylinositol breakdown. 2. The enzyme pathway involved. 3. Possible second messengers. 4. Inositol analogs as inhibitors of the breakdown and of the synthesis of phosphatidylinositol. 5. The roles of phosphatidylinositol breakdown, of the inositol liberated, and of phosphatidic acid turnover in the stimulation by acetylcholine of the protein synthesis-secretion cycle in the exocrine pancreas and in the stimulation by acetylcholine of NaK-ATPase activity in the avian salt gland. 6. The significance of similar changes in phospholipid metabolism which occur in brain in response to acetylcholine and some other neurotransmitters. Methodology includes work with the mouse pancreas in vivo and in vitro; incubation of slices of goose salt gland and guinea pig cerebral cortex, subcellular fractionation, studies of enzyme pathways in cell membrane preparations, thin-layer and gas chromatographic analyses, the use of radioisotopes, and the synthesis of inositol analogs.